Yes, that's what I've tried to imply. You name things, so you can discuss them in more abstract terms, so you can form a social & legal framework around those concepts.
> My whole point is that not having to define such relationships and their expectations is a reason to forbid them culturally.
>> [...] not having to define [...] is a reason to forbid [...].
Suppress the concept. "We don't talk about that."
> How did that work before most people knew how to write?
How did people enter agreements?
> Personally, I'm more of the opinion that cultural features are memetic, and that memes are not uniformly successfully propagated.
Agree. It's also how dictatorships rise. Another form of oppression that concentrates power and fires back at the group who have initially supported it. Another lose-lose.
Societies often overoptimize for a local maximum.